Effect of pilocarpine presbyopia treatment on anterior segment biometry

Abstract

Purpose : To investigate the effects of pilocarpine for presbyopia treatment on pupil and crystalline lens shape using a custom-made OCT system. The study can provide information on the mechanism of action of pilocarpine when used as a topical therapy for presbyopia correction.

Methods : This is a prospective study on 5 eyes of 5 subjects of age 40, 44, 46, 47 and 51 years. Subjects underwent imaging with a custom-made OCT system that combines a fixation target with adjustable vergence (Ruggeri et al, Biomed Opt Exp 2016). Subjects were imaged with accommodative targets simulating 0 D (distance), 1.5 D (66 cm), and 2.5 D (40 cm) at baseline and 1 hour after administration of 1% and 1.25% pilocarpine. Best corrected distance visual acuity (BCDVA) and best corrected near visual acuity (BCNVA) at 40 cm and 66 cm were assessed in all conditions. All experiments were performed in photopic conditions. Pupillary diameter and lens thickness were extracted from the OCT images.

Results : The pupil constricted after administration of pilocarpine compared to baseline in all subjects and independently of the accommodative demand (Figure A). Mean decrease in pupil diameter across accommodative demands and subjects was 1.56 mm and 1.51 mm at concentrations of pilocarpine of 1% and 1.25%, respectively. We found no significant changes in lens thickness with pilocarpine concentration and accommodative demand in the presbyopic subjects (44, 46, 47, 51 year old). Lens thickness increased significantly in the pre-presbyopic subject (40 year old) with pilocarpine, with a mean lens thickness change across accommodative demands of +0.08mm and +0.25 mm for 1% and 1.25% concentrations, respectively. Baseline average BCVA at distance, 66 cm and 40 cm were logMAR -0.06, 0.21 and 0.29, respectively. On average, subjects gained 1-line in BCNVA at 40 cm for both pilocarpine concentrations (0.16 and 0.19 for 1% and 1.25% respectively) but lost 2 letters of BCDVA (-0.02 logMAR) with 1% and 4 letters (0.02 logMAR) with 1.25%.

Conclusions : Preliminary results suggest that concentrations of 1% and 1.25% of pilocarpine have comparable effect on pupil diameter and visual acuity in presbyopic eyes. For these subjects, improved near visual function seems only achieved by an increased in depth of focus secondary to pupil constriction. In the pre-presbyopic subject, pilocarpine induced both pupil constriction and a change in lens shape.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.